Recent reports indicate that several mechanisms may operate independently or jointly in the induction and maintenance of specific acquired immunological tolerance, and that one may predominate over the other depending on various factors such as (1) the age of the host at the time of the induction of tolerance, (2) the nature of the antigen in question. In addition there is some evidence that a given clone of antibody producing cells can be preferentially suppressed or eliminated during the induction of tolerance. It is the purpose of this proposed research to: (1) define the tolerant state to human gamma globulin in mice induced when the mice are neonates; (2) determine the effect of the induction of tolerance on different antibody producing clones; and (3) determine the nature of the genetic information expressed after the spontaneous loss of tolerance. BIBLIOGRAPHIC REFERENCES: Emmons, R.P. and Benjamin, D. C. Isolation and Characterization of a Concanavalin-A Receptor from Rabbit Thymocytes. Fed. Proc. 34:1012, 1975 (abstract).